Motion analysis apparatus, motion analysis system, motion analysis method, recording medium, and display method

ABSTRACT

A golf swing analysis apparatus detects a state of a shaft of a golf club by using an output from an inertial sensor, calculates a relative rotation angle of the shaft which changes about an axis of the shaft until the shaft transitions from a first state to a second state due to a swing of the shaft, and compares the calculated relative rotation angle with a reference relative rotation angle in a reference swing which is used as a reference, with respect to at least one of a change range of the relative rotation angle, the required time from the first state to a state in which the relative rotation angle becomes the maximum, and the maximum value of the relative rotation angle, and outputs a comparison result.

BACKGROUND

1. Technical Field

The present invention relates to a motion analysis apparatus, a motion analysis system, a motion analysis method, a recording medium, and a display method.

2. Related Art

As an analysis apparatus for checking a swing action in golf, as disclosed in JP-A-2008-73210, an analysis apparatus has been proposed in which an inertial sensor having a gyro sensor, an acceleration sensor, or the like is attached to a golf club, and a swing action is analyzed on the basis of an output signal from the inertial sensor measuring a swing performed by a user.

However, in the technique disclosed in JP-A-2008-73210, a direction of a club head or rotation of a shaft in each swing performed by the user can be specified, but information for determining whether or not a swung golf club is suitable for the user cannot be obtained.

SUMMARY

An advantage of some aspects of the invention is to determine a golf club suitable for a user by analyzing an action of swinging the golf club.

The advantage can be achieved by the following configurations.

Application Example 1

A motion analysis apparatus according to this application example includes a detection portion that detects a state of a shaft of an exercise equipment by using an output from an inertial sensor; a calculation portion that calculates a relative rotation angle of the shaft which changes about an axis of the shaft until the shaft transitions from a first state to a second state due to a swing of the exercise equipment; and a comparison calculation portion that compares the relative rotation angle calculated by the calculation portion with a reference relative rotation angle in a reference swing which is used as a reference, with respect to at least one of a change range of the relative rotation angle, the required time from the first state to a state in which the relative rotation angle becomes the maximum, and the maximum value of the relative rotation angle, and outputs a comparison result.

According to this configuration, a relative rotation angle of the shaft which changes about an axis of the shaft until the shaft transitions from a first state to a second state due to a swing of the exercise equipment is calculated, and a first relative rotation angle calculated by the calculation portion is compared with a second relative rotation angle in a reference swing, with respect to at least one of a change range of a relative rotation angle from the first state to the second state, the required time from the first state to a state in which the relative rotation angle becomes the maximum, and the maximum value of the relative rotation angle. Therefore, in the transition from the first state to the second state, a swing action using the exercise equipment is compared with the reference swing in terms of the relative rotation angle, and thus it is possible to determine whether or not the exercise equipment is appropriate.

Application Example 2

In the motion analysis apparatus according to the application example, the external apparatus may be a golf club, the first state may be a top state, and the second state may be an impact state.

Application Example 3

In the motion analysis apparatus according to the application example, it is preferable that the reference swing is a swing using a golf club which is different from the golf club.

According to this configuration, swing actions using golf clubs having different characteristics are compared with each other, and thus it is possible to compare swing actions based on a difference between the golf clubs.

Application Example 4

In the motion analysis apparatus according to the application example, it is preferable that the reference swing is a swing performed by a user who is different from a user performing the swing.

According to this configuration, it is possible to compare swing actions based on a difference between persons performing swings.

Application Example 5

In the motion analysis apparatus according to the application example, it is preferable that the comparison calculation portion normalizes the relative rotation angle in the first state as an initial value, and compares a relative rotation angle calculated with the passage of transition time from the first state to the second state, with the reference relative rotation angle.

According to this configuration, it is possible to compare a first relative rotation angle with a second relative rotation angle with the passage of transition time from the first state to the second state by using a relative rotation angle in the first state as a reference.

Application Example 6

It is preferable that the motion analysis apparatus according to the application example further includes a display portion that displays the comparison result.

According to this configuration, it is possible to visually recognize a comparison result.

Application Example 7

A motion analysis system according to this application example includes the motion analysis apparatus described above and an inertial sensor.

According to this configuration, a relative rotation angle of the shaft which changes about an axis of the shaft until the shaft transitions from a first state to a second state due to a swing of the exercise equipment is calculated, and a first relative rotation angle calculated by the calculation portion is compared with a second relative rotation angle in a reference swing, with respect to at least one of a change range of the relative rotation angle from the first state to the second state, the required time from the first state to a state in which the relative rotation angle becomes the maximum, and the maximum value of the relative rotation angle. Therefore, in the transition from the first state to the second state, a swing action using the exercise equipment is compared with the reference swing in terms of the relative rotation angle, and thus it is possible to determine whether or not the exercise equipment is appropriate.

Application Example 8

A motion analysis method according to this application example includes detecting a state of a shaft of an exercise equipment by using an output from an inertial sensor; calculating a relative rotation angle of the shaft which changes about an axis of the shaft until the shaft transitions from a first state to a second state due to a swing of the exercise equipment; and comparing the calculated relative rotation angle with a reference relative rotation angle in a reference swing which is used as a reference, with respect to at least one of a change range of the relative rotation angle, the required time from the first state to a state in which the relative rotation angle becomes the maximum, and the maximum value of the relative rotation angle, and outputting a comparison result.

According to this method, a relative rotation angle of the shaft which changes about an axis of the shaft until the shaft transitions from a first state to a second state due to a swing of the exercise equipment is calculated, and a calculated first rotation angle is compared with a second relative rotation angle in a reference swing, with respect to at least one of a change range of the relative rotation angle from the first state to the second state, the required time from the first state to a state in which the relative rotation angle becomes the maximum, and the maximum value of the relative rotation angle. Therefore, in the transition from the first state to the second state, a swing action using the exercise equipment is compared with the reference swing in terms of the relative rotation angle, and thus it is possible to determine whether or not the exercise equipment is appropriate.

Application Example 9

A motion analysis program according to this application example causes a computer to execute detecting a state of a shaft of an exercise equipment by using an output from an inertial sensor; calculating a relative rotation angle of the shaft which changes about an axis of the shaft until the shaft transitions from a first state to a second state due to a swing of the exercise equipment; and comparing the calculated relative rotation angle with a reference relative rotation angle in a reference swing which is used as a reference, with respect to at least one of a change range of the relative rotation angle, the required time from the first state to a state in which the relative rotation angle becomes the maximum, and the maximum value of the relative rotation angle, and outputting a comparison result.

According to this configuration, a relative rotation angle of the shaft which changes about an axis of the shaft until the shaft transitions from a first state to a second state due to a swing of the exercise equipment is calculated, and a calculated first rotation angle is compared with a second relative rotation angle in a reference swing, with respect to at least one of a change range of the relative rotation angle from the first state to the second state, the required time from the first state to a state in which the relative rotation angle becomes the maximum, and the maximum value of the relative rotation angle. Therefore, in the transition from the first state to the second state, a swing action using the exercise equipment is compared with the reference swing in terms of the relative rotation angle, and thus it is possible to determine whether or not the exercise equipment is appropriate.

Application Example 10

A recording medium according to this application example records a program causing a computer to execute detecting a state of a shaft of an exercise equipment by using an output from an inertial sensor; calculating a relative rotation angle of the shaft which changes about an axis of the shaft until the shaft transitions from a first state to a second state due to a swing of the exercise equipment; and comparing the calculated relative rotation angle with a reference relative rotation angle in a reference swing which is used as a reference, with respect to at least one of a change range of the relative rotation angle, the required time from the first state to a state in which the relative rotation angle becomes the maximum, and the maximum value of the relative rotation angle, and outputting a comparison result.

According to this configuration, a relative rotation angle of the shaft which changes about an axis of the shaft until the shaft transitions from a first state to a second state due to a swing of the exercise equipment is calculated, and a calculated first relative rotation angle is compared with a second relative rotation angle in a reference swing, with respect to at least one of a change range of the relative rotation angle from the first state to the second state, the required time from the first state to a state in which the relative rotation angle becomes the maximum, and the maximum value of the relative rotation angle. Therefore, in the transition from the first state to the second state, a swing action using the exercise equipment is compared with the reference swing in terms of the relative rotation angle, and thus it is possible to determine whether or not the exercise equipment is appropriate.

Application Example 11

A display method according to this application example includes displaying transition of a relative rotation angle of a shaft which changes about an axis of the shaft until the shaft transitions from a first state to a second state due to a swing of an exercise equipment, and reference transition of a relative rotation angle in a reference swing which is used as a reference, in an overlapping manner by normalizing the relative rotation angle in the first state as an initial value.

According to this configuration, a relative rotation angle of the shaft which changes about an axis of the shaft until the shaft transitions from a first state to a second state due to a swing of the exercise equipment is calculated, and a calculated first rotation angle is compared with a second relative rotation angle in a reference swing, with respect to at least one of a change range of the relative rotation angle from the first state to the second state, the required time from the first state to a state in which the relative rotation angle becomes the maximum, and the maximum value of the relative rotation angle. Therefore, in the transition from the first state to the second state, a swing action using the exercise equipment is compared with the reference swing in terms of the relative rotation angle, and thus it is possible to determine whether or not the exercise equipment is appropriate.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements.

FIG. 1 is a diagram illustrating a golf swing analysis apparatus according to an embodiment.

FIG. 2 is a diagram for explaining a three-dimensional motion analysis model.

FIG. 3 is a diagram for explaining swing actions.

FIG. 4 is a diagram for explaining a golf club to which an inertial sensor is attached.

FIG. 5A is a diagram in which angular velocities are displayed in a graph.

FIG. 5B is a diagram in which a norm is displayed in a graph.

FIG. 5C is a diagram in which a derivative value based on the norm is displayed in a graph.

FIG. 6 is a diagram illustrating a temporal change of a shaft rotation angle from swing starting to impact.

FIG. 7 is a diagram illustrating a configuration of a calculation processing circuit.

FIG. 8 is a diagram illustrating an image representing a swing action.

FIG. 9 is a graph illustrating a relative rotation angle over time from a top to impact.

FIG. 10 is a comparative image in a case where the same user performs swings.

FIG. 11 is a comparative image in a case where a plurality of user perform swings.

FIG. 12 is a flowchart illustrating examples of procedures of a process of detecting a timing at which a user hit a ball.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, an embodiment of the invention will be described with reference to the drawings.

Embodiment (1) Configuration of Golf Swing Analysis Apparatus

FIG. 1 is a diagram schematically illustrating a configuration of a golf swing analysis apparatus (motion analysis apparatus) 11 according to an embodiment of the invention. The golf swing analysis apparatus 11 includes a display device 19, an image processing circuit 18, a calculation processing circuit 14, a storage device 16, an input device 21, and an interface circuit 15.

In the present embodiment, a motion analysis system includes the golf swing analysis apparatus 11 and an inertial sensor 12. A computer employs a personal computer.

For example, an acceleration sensor or a gyro sensor (angular velocity sensor) is incorporated into the inertial sensor 12. The acceleration sensor can detect respective accelerations in three-axis directions which are orthogonal to each other. The gyro sensor can detect respective angular velocities about three axes which are orthogonal to each other. The inertial sensor 12 outputs a detection signal based on detected information for each predetermined sampling timing. The golf swing analysis apparatus 11 analyzes a swing on the basis of the detection signal output from the inertial sensor 12.

The inertial sensor 12 is attached to an exercise equipment such as a golf club 13. The golf club 13 is provided with a shaft 13 a corresponding to a shaft portion, and a grip 13 b. The grip 13 b is formed to be held when the golf club 13 is swung. The grip 13 b is formed to have the same axis as an axis of the shaft 13 a. A club head 13 c which is a ball hitting portion is provided at a front end of the shaft 13 a. An aspect is assumed in which the inertial sensor 12 is attached to the shaft 13 a or the grip 13 b of the golf club 13. The inertial sensor 12 is preferably fixed to the golf club 13 so as not to be relatively moved.

The golf swing analysis apparatus 11 includes the calculation processing circuit 14. The inertial sensor 12 is connected to the calculation processing circuit 14. The calculation processing circuit 14 is connected to the predetermined interface circuit 15. The interface circuit 15 may be connected to the inertial sensor 12 in a wired manner, and may be connected to the inertial sensor 12 in a wireless manner. A detection signal output from the inertial sensor 12 is supplied to the calculation processing circuit 14.

The calculation processing circuit 14 is connected to the storage device 16. The storage device 16 may store a program 17, for example, a golf swing analysis software program (motion analysis program), and related data. The calculation processing circuit 14 executes a program such as the golf swing analysis software program. The storage device 16 may be formed of a dynamic random access memory (DRAM), a large-capacity storage device unit, a nonvolatile memory, and the like. For example, the DRAM temporarily holds the golf swing analysis software program. The golf swing analysis software program and data are preserved in the large-capacity storage device unit such as a hard disk drive (HDD). A relatively small-capacity program such as BIOS, or data is stored in the nonvolatile memory.

The image processing circuit 18 is connected to the calculation processing circuit 14. The calculation processing circuit 14 sends predetermined image data to the image processing circuit 18. The image processing circuit 18 is connected to the display device 19. The image processing circuit 18 is connected to a predetermined interface circuit (not illustrated). The image processing circuit 18 sends an image signal to the display device 19 according to input image data. An image specified by the image signal is displayed on a screen of the display device 19. In the present embodiment, a liquid crystal display or other flat panel displays are used as the display device 19. The display device 19 corresponds to a display portion.

The display device 19 may be provided separately from a personal computer. There may be an aspect in which the display device 19 is a head mounted display, smart glasses, or a wrist device, and image data is transmitted from the personal computer to the display device 19 by using near field communication.

The calculation processing circuit 14 is connected to the input device 21. As the input device 21, a keyboard or a touch panel which allows a key operation or a pointing operation to be performed, or a voice input device which can recognize a voice may be used. Information which is input from the input device 21 is sent to the calculation processing circuit 14.

(2) Motion Analysis Model

The calculation processing circuit 14 defines a virtual space which is a three-dimensional space. The three-dimensional space specifies a real space. FIG. 2 is a diagram for explaining a three-dimensional motion analysis model.

The three-dimensional space has an absolute reference coordinate system (global coordinate system) Σxyz. A three-dimensional motion analysis model 26 is built in the three-dimensional space according to the absolute reference coordinate system Σxyz. A rod 27 of the three-dimensional motion analysis model 26 is point-restrained to a fulcrum 28 (coordinate x). The rod 27 operates as a pendulum about the fulcrum 28 in a three-dimensional manner. A position of the fulcrum 28 can be moved. Here, a position of the club head 13 c is specified by a coordinate xh according to the absolute reference coordinate system Σxyz.

The three-dimensional motion analysis model 26 is obtained by modeling the golf club 13 during a swing. The rod 27 of the pendulum projects the shaft 13 a of the golf club 13. The fulcrum 28 of the rod 27 projects the grip 13 b. The inertial sensor 12 is fixed to the rod 27. A position of the inertial sensor 12 is specified by a coordinate xs according to the absolute reference coordinate system Σxyz. The inertial sensor 12 outputs an acceleration signal and an angular velocity signal. The acceleration signal specifies an acceleration including the gravitational acceleration g as follows.

({umlaut over (x)} _(s) −g)

The angular velocity signal specifies an angular velocity.

The calculation processing circuit 14 fixes a local coordinate system Σs to the inertial sensor 12. The origin of the local coordinate system Σs is set to the origin of detection axes of the inertial sensor 12. A y axis of the local coordinate system Σs matches an axis of the shaft 13 a. An x axis of the local coordinate system Σs matches a ball hitting direction specified by a direction of a face (ball hitting surface). Therefore, a position l_(sj) of the fulcrum is specified by (0, l_(sjy), 0) according to the local coordinate system Σs. Similarly, a position l_(sh) of the club head 13 c is specified by (0, l_(shy), 0).

Next, a swing action in golf will be described. FIG. 3 is a diagram for explaining swing actions.

The swing actions performed by a user 200 of the golf swing analysis apparatus 11 include actions reaching impact (ball hitting) at which a golf ball 250 is hit through respective states of halfway back at which the shaft 13 a of the golf club 13 becomes horizontal during a backswing after starting a swing (backswing), a top at which the swing changes from the backswing to a downswing, and halfway down at which the shaft 13 a of the golf club 13 becomes horizontal during the downswing.

(3) Detection of Swing Rhythm

The golf swing analysis apparatus 11 may detect a swing rhythm of the user 200 on the basis of angular velocities detected by the inertial sensor 12.

As illustrated in FIG. 4, if the inertial sensor 12 is attached to the vicinity of the grip 13 b, and the user 200 performs a swing with the held golf club 13, a swing action of hitting the golf ball 250 is analyzed. The inertial sensor 12 may be mounted in a casing (not illustrated), and the casing may be attachably and detachably installed at the golf club 13. There may be an aspect in which the inertial sensor 12 is directly attached to the golf club 13 or the user 200.

The inertial sensor 12 is attached so that an X axis is a direction parallel to the shaft, a Y axis is along a swing direction, and a Z axis is along a direction perpendicular to a swing plane.

The swing direction indicates a target ball hitting direction, and also includes a direction orthogonal to a face surface of the head as a ball hitting portion of the golf club 13, a ball hitting direction which is set in advance by the user 200, a direction in which a position of the user 200 is connected to a cup, and the like.

FIG. 5A is a diagram in which three-axis angular velocities x(t), y(t) and z(t) are displayed in a graph on the basis of data acquired in a data acquisition period (for 5 seconds) when the user 200 performs a full-swing with the golf club 13. In FIG. 5A, a transverse axis expresses time (msec), and a longitudinal axis expresses angular velocity (dps).

FIG. 5B is a diagram in which a norm n₀(t) which is a sum of the magnitudes of the three-axis angular velocities x(t), y(t) and z(t) in FIG. 5A is computed according to the following equation, and then a norm n(t) scale-converted (normalized) to 0 to 100 is displayed in a graph. In FIG. 5B, a transverse axis expresses time (msec), and a longitudinal axis expresses a norm (scale-converted to 0 to 100) of the angular velocity.

n ₀(t)=√{square root over (x(t)² +y(t)² +z(t)²)}

FIG. 5C is a diagram in which a derivative dn(t) is calculated on the basis of the norm n(t) of the three-axis angular velocities in FIG. 5B, and is displayed in a graph. In FIG. 5C, a transverse axis expresses time (msec), and a longitudinal axis expresses a derivative value of the norm of the three-axis angular velocities.

Here, a description will be made of a process of detecting a timing at which the user 200 hit the ball with reference to FIG. 12.

First, the calculation processing circuit 14 computes a combined value n₀(t) of angular velocities at each time point t by using acquired angular velocity data (angular velocity data for each time point t) (step S300). For example, if the angular velocity data items at the time point t are respectively indicated by x(t), y(t), and z(t), the combined value n₀(t) of the angular velocities is computed according to the following equation.

n ₀(t)=√{square root over (x(t)² +y(t)² +z(t)²)}

Next, the calculation processing circuit 14 converts the combined value n₀(t) of the angular velocities at each time point t into a combined value n(t) which is normalized (scale-conversion) within a predetermined range (step S310). For example, if the maximum value of the combined value of the angular velocities in an acquisition period of measured data is max(n₀), the combined value n₀(t) of the angular velocities is converted into the combined value n(t) which is normalized within a range of 0 to 100 according to the following equation.

${n(t)} = \frac{100 \times {n_{0}(t)}}{\max \left( n_{0} \right)}$

Next, the calculation processing circuit 14 computes a derivative dn(t) of the normalized combined value n(t) at each time point t (step S320). For example, if a cycle for measuring three-axis angular velocity data items is indicated by Δt, the derivative (difference) dn(t) of the combined value of the angular velocities at the time point t is computed by using the following equation.

dn(t)=n(t)−n(t−Δt)

Finally, of time points at which a value of the derivative dn(t) of the combined value becomes the maximum and the minimum, the calculation processing circuit 14 specifies the earlier time point as a ball hitting timing (step S330). It is considered that swing speed is the maximum at the moment of ball hitting in a typical golf swing. Since it is considered that a value of the combined value of the angular velocities also changes according to a swing speed, a timing at which a derivative value of the combined value of the angular velocities is the maximum or the minimum (that is, a timing at which the derivative value of the combined value of the angular velocities is a positive maximum value or a negative minimum value) in a series of swing actions can be captured as the ball hitting (impact) timing. Since the golf club 13 vibrates due to the ball hitting, a timing at which a derivative value of the combined value of the angular velocities is the maximum and a timing at which a derivative value of the combined value of the angular velocities is the minimum may occur in pairs, and, of the two timings, the earlier timing may be the moment of the ball hitting.

In a case where the user 200 performs a swing action, a series of rhythms is expected in which the user 200 stops the golf club 13 at a top position, performs a downswing, hits the ball, and performs follow-through. Therefore, according to the flowchart illustrated in FIG. 12, the calculation processing circuit 14 may detect candidates of a timing at which the user 200 hit the ball, determine whether or not measured data before and after the detected timing matches the rhythm, fix the detected timing as a timing at which the user 200 hit the ball in a case where the data matches the rhythm, and detect the next candidate in a case where the data does not match the rhythm.

In the flowchart illustrated in FIG. 12, the calculation processing circuit 14 detects a ball hitting timing by using the three-axis angular velocity data items, but may similarly detect a ball hitting timing by using three-axis acceleration data items.

Here, referring to FIGS. 5B and 5C again, a description will be made of specifying of an event. For example, a time point at which a peak value of the norm is obtained is specified as an impact timing, a time point at which the minimum value is obtained before impact is specified as a top timing, and a time point at which the minimum value is obtained after impact is specified as a finish timing. Further, a time point at which the minimum value is obtained before the top is specified as a swing starting timing. As mentioned above, details of a method in which a swing rhythm is analyzed on the basis of transition of the norm, and each event is specified are disclosed in, for example, JP-A-2012-254206.

The golf swing analysis apparatus 11 may detect a relative rotation angle (shaft rotation angle) θ about the shaft axis in a swing action on the basis of angular velocities detected by the inertial sensor 12.

FIG. 6 is a diagram illustrating an example of a temporal change of a shaft rotation angle from starting of a swing (starting of a backswing) to impact in correlation with each specified swing. In FIG. 6, a transverse axis expresses time (s), and a longitudinal axis expresses a shaft rotation angle (deg). FIG. 6 illustrates a shaft rotation angle θ_(top) at top with the time of starting a swing (the time of starting a backswing) as a reference timing (at which the shaft rotation angle is 0°).

In FIG. 6, a change rate of the relative rotation angle θ from a top to impact is higher than a change rate thereof from swing starting to the top. In the golf swing analysis apparatus 11, the calculation processing circuit 14 has a function of analyzing the relative rotation angle θ in detail by focusing on a change thereof from the top to impact.

The relative rotation angle may be calculated on the basis of one swing action, and may be calculated on the basis of an average value of a plurality of swing actions.

(4) Configuration of Calculation Processing Circuit

FIG. 7 schematically illustrates a configuration of the calculation processing circuit 14. The calculation processing circuit 14 includes a first detection portion 31 and a second detection portion 32. The first detection portion 31 and the second detection portion 32 are connected to the inertial sensor 12. An output from the inertial sensor 12 is supplied to the first detection portion 31 and the second detection portion 32.

The first detection portion 31 detects an initial angle of the grip 13 b about an axis (the same axis as the axis of the shaft 13 a) of the grip 13 b on the basis of the output from the inertial sensor 12. During the detection, the first detection portion 31 acquires an angular velocity at address in an axial direction (y axial direction) which is parallel to the shaft 13 a from the inertial sensor 12. The first detection portion 31 sets the acquired angular velocity to an initial value. Here, an angular velocity about the y axis is not generated at address, and, thus, if the angular velocity is set to “0 (zero)”, an angle is also set to “0° (zero degrees)” (=initial angle).

The second detection portion 32 detects a relative rotation angle θn (where n=1, . . . , and N) of the grip 13 b about the axis from the initial angle of “0°” on the basis of the output from the inertial sensor 12. As shown in the following equation, a calculated change amount is accumulated. Here, N indicates the number of samples (the same applies hereinafter). In the present embodiment, regarding the relative rotation angle θ, one rotation direction is expressed as a positive value with respect to the angle of “0°”, and the other rotation direction is expressed as a negative value.

θ₀ = 0 $\theta_{m} = {\sum\limits_{n = 1}^{m}{{\omega_{n} \cdot {dt}}\mspace{11mu} \left( {1 \leq m < N} \right)}}$

As a result, a change amount from an initial position is calculated at a time point at which the change amount is accumulated in the unit time. In the above-described way, the relative rotation angle θ of the grip 13 b is specified along the time axis.

The calculation processing circuit 14 includes an attitude detection portion 34. The attitude detection portion 34 is connected to the inertial sensor 12. An output from the inertial sensor 12 is supplied to the attitude detection portion 34. Herein, the output from the inertial sensor 12 includes accelerations respectively detected along the orthogonal three axes and angular velocities respectively detected about the orthogonal three axes. The attitude detection portion 34 detects an attitude of the golf club 13 on the basis of the output from the inertial sensor 12, and detects a swing rhythm on the basis of a norm of the three-axis angular velocities.

When a position is detected, the attitude detection portion 34 calculates accelerations of the grip 13 b according to the following equation. When the accelerations are calculated, the attitude detection portion 34 specifies a position l_(sj) of the grip 13 b according to the local coordinate system Σs specific to the inertial sensor 12. The attitude detection portion 34 acquires position information from the storage device 16. The position l_(sj) of the grip 13 b is stored in the storage device 16 in advance. The position l_(sj) of the grip 13 b may be designated via, for example, the input device 21.

α_(sj)=α_(s)+{dot over (ω)}_(s) ×l _(sj)×ω_(s)×(ω_(s) ×l _(sj))+g

The attitude detection portion 34 calculates a movement speed of the grip 13 b on the basis of the calculated accelerations. Here, an integration process is performed on the accelerations at a predefined sampling interval dt according to the following equation.

V_(sj)(0) = 0 ${V_{sj}(t)} = {\sum\limits_{n = 1}^{t}{{{\alpha_{sj}(n)} \cdot {dt}}\mspace{14mu} \left( {{t = 1},\ldots \mspace{14mu},N} \right)}}$

The attitude detection portion 34 calculates the position of the grip 13 b on the basis of the calculated speed. Here, an integration process is performed on the speed at the predefined sampling interval dt according to the following equation.

${P_{sj}(t)} = {\sum\limits_{n = 1}^{t}{{{V_{sj}(n)} \cdot {dt}}\mspace{14mu} \left( {{t = 1},\ldots \mspace{14mu},N} \right)}}$

Similarly, the attitude detection portion 34 detects a position of the club head 13 c according to the following equation. When the position is detected, the attitude detection portion 34 specifies a position l_(sh) of the club head 13 c according to the local coordinate system Σs specific to the inertial sensor 12. When the position is specified, the attitude detection portion 34 acquires position information from the storage device 16. The position l_(sh) of the club head 13 c is stored in the storage device 16 in advance. The position l_(sh) of the club head 13 c may be designated via, for example, the input device 21.

$\begin{matrix} {{\alpha_{sh} = {\alpha_{s} + {{\overset{.}{\omega}}_{s} \times l_{sh}} + {\omega_{s} \times \left( {\omega_{s} \times l_{sh}} \right)} + g}}} \\ {{V_{sh}(0)} = 0} \\ {{V_{sh}(t)} = {\sum\limits_{n = 1}^{t}{{{\alpha_{sh}(n)} \cdot {dt}}\mspace{14mu} \left( {{t = 1},\ldots \mspace{14mu},N} \right)}}} \\ {{P_{sh}(t)} = {\sum\limits_{n = 1}^{t}{{{V_{sh}(n)} \cdot {dt}}\mspace{14mu} \left( {{t = 1},\ldots \mspace{14mu},N} \right)}}} \end{matrix}$

The calculation processing circuit 14 includes a swing image data generation portion 35. The swing image data generation portion 35 is connected to the attitude detection portion 34. An output from the attitude detection portion 34 is supplied to the swing image data generation portion 35. The swing image data generation portion 35 specifies a movement trajectory of the golf club 13 on the basis of the position of the grip 13 b and the position of the club head 13 c calculated by the attitude detection portion 34. An image (FIG. 8) representing a swing action is generated on the basis of the specified movement trajectory. The image is output as image data from the swing image data generation portion 35.

The calculation processing circuit 14 includes a standing-still detection portion 36. The standing-still detection portion 36 is connected to the inertial sensor 12. An output from the inertial sensor 12 is supplied to the standing-still detection portion 36. Herein, the output from the inertial sensor 12 includes accelerations respectively detected along the orthogonal three axes and angular velocities respectively detected about the orthogonal three axes.

The standing-still detection portion 36 determines a standing still state of the golf club 13 on the basis of an output from the inertial sensor 12. If the output from the inertial sensor 12 is less than a threshold value, the standing-still detection portion 36 determines that the golf club 13 is in a standing still state. The standing still state of the golf club 13 indicates address which is one of the events in the swing rhythm. The threshold value may be set to a value which can eliminate the influence of a detection signal indicating minute vibration such as body movement.

If a standing still state is confirmed for a predetermined period, the standing-still detection portion 36 outputs a standing-still notification signal. The standing-still notification signal is sent to the first detection portion 31, the second detection portion 32, and the attitude detection portion 34. The first detection portion 31 sets an angular position to an initial position of “0°” in response to reception of the standing-still notification signal. The second detection portion 32 starts to calculate the relative rotation angle θ in response to reception of the standing-still notification signal. The attitude detection portion 34 starts to detect an attitude of the golf club 13 in response to reception of the standing-still notification signal.

Herein, the standing-still detection portion 36 may refer to an inclined angle of the golf club 13 so as to determine a standing still state thereof. At this time, the standing-still detection portion 36 calculates an inclined angle, that is, an attitude of the golf club 13 on the basis of coordinates of the grip 13 b and coordinates of the club head 13 c. The standing-still detection portion 36 determines an attitude of the golf club 13 at address on the basis of the calculated inclined angle. It is determined whether or not the inclined angle is included in a predetermined inclined angle range. The standing-still detection portion 36 starts to determine a standing still state of the golf club 13 after an attitude of the golf club 13 at address is established.

The calculation processing circuit 14 includes an event detection portion 37. The event detection portion 37 is connected to the attitude detection portion 34. An output from the attitude detection portion 34 is supplied to the event detection portion 37. The event detection portion 37 specifies each event in the swing rhythm on the basis of an attitude of the golf club 13. For example, the event detection portion 37 detects an axis (that is, an axis of the shaft 13 a) of the grip 13 b disposed to be parallel to the ground surface. In the above-described way, halfway back during a backswing can be specified.

The event detection portion 37 may specify the events in the swing rhythm, such as a top, impact, and a finish on the basis of a change in the norm of three-axis angular velocities over time.

The calculation processing circuit 14 includes a calculation portion 38. The calculation portion 38 is connected to the event detection portion 37 and the second detection portion 32. An output from the event detection portion 37 and an output from the second detection portion 32 are supplied to the calculation portion 38.

The calculation portion 38 extracts a change amount of the relative rotation angle θ corresponding to the events from a top to impact, detected by the event detection portion 37, and calculates the relative rotation angle θ corresponding to a temporal change reaching impact (second state) from a top (first state) with the relative rotation angle θ at the top as “0° (zero degrees)” (=initial value) at a predetermined time interval. The calculation portion 38 is connected to a comparison calculation portion 39. An output from the calculation portion 38 is supplied to the comparison calculation portion 39.

Data regarding the relative rotation angle θ calculated by the calculation portion 38 is set to be stored in the storage device 16 as a reference swing which is used as a reference in a case of comparison in correlation with information which is input in advance with regard to the golf club 13 which is used or the user 200 having performed a swing.

The calculation processing circuit 14 includes the comparison calculation portion 39. The comparison calculation portion 39 is connected to the calculation portion 38. An output from the calculation portion 38 is supplied to the comparison calculation portion 39.

The comparison calculation portion 39 compares data regarding the relative rotation angle (first relative rotation angle) θ calculated by the calculation portion 38 with data regarding a relative rotation angle (second relative rotation angle) θ obtained on the basis of the reference swing, and outputs a comparison result to a first image data generation portion 33.

Here, FIG. 9 is a graph indicating the relative rotation angle θ over time from a top as an initial value, that is, a starting point (t=0) to impact (t=t2) in a swing. This graph expresses elapsed time in a transverse axis direction, and expresses the relative rotation angle θ in a longitudinal axis direction. The origin is normalized so that the relative rotation angle θ at the top, that is, the starting point is “0° (zero degrees)”. A description will be made of items (hereinafter, referred to as comparative items) which are compared with the reference swing by referring to the graph.

The comparison calculation portion 39 employs the following items as comparative items regarding the relative rotation angle θ.

1. A change range (simply referred to as a range) of the relative rotation angle θ from a top to impact

2. Required time until the relative rotation angle θ becomes the maximum with a top as a starting point

3. The maximum value of the relative rotation angle θ

In FIG. 9, a range of the relative rotation angle θ from a top to impact Q is indicated by θ2. The time required for the relative rotation angle θ to become the maximum is indicated by t1. The maximum value P of the relative rotation angle θ is indicated by θ1.

The comparison calculation portion 39 compares a swing performed by the user 200 with the reference swing with respect to at least one of the above-described items.

Referring to FIG. 7 again, the calculation processing circuit 14 includes the first image data generation portion 33. The first image data generation portion 33 generates an image which visually displays the relative rotation angle θ. The first image data generation portion 33 generates an image which allows a difference from the reference swing to be visually recognized on the basis of a comparison result output from the comparison calculation portion 39.

Such an image is assumed to be a comparative image generated according to a display method in which a graph indicating transition of the relative rotation angle θ over time, calculated by the calculation portion 38, from the top as the starting point to the impact with the relative rotation angle at the top as “0° (zero degrees)” overlaps a graph indicating transition of the relative rotation angle θ over time in the reference swing.

Here, examples of the comparative image will be described with reference to FIGS. 10 and 11.

FIG. 10 illustrates a comparative image generated by the first image data generation portion 33 in a case where the same user 200 performs swings by using different golf clubs 13. In other words, a swing performed by the user 200 by using a driver A as the golf club 13 is compared with swings performed by the user 200 by using a driver B and a driver C having characteristics which are different from characteristics of the driver A as reference swings.

As illustrated in FIG. 10, regarding the driver A (θ1A) and the driver B (θ1B), the maximum value of the relative rotation angle θ in the driver A is greater than that in the driver B, but ranges (θ2A and θ2B) of the relative rotation angle θ, and the time required for the relative rotation angle θ to become the maximum is respectively the same as each other. The driver C (θ1C) has a shorter time required for the relative rotation angle θ to become the maximum than that of each of the drivers A and B, and also has a smaller maximum value of the relative rotation angle θ.

Since the relative rotation angle θ transitions depending on the characteristics of the golf club 13, the user 200 can select the golf club 13 suitable for the user 200 from among the drivers A, B and C based on the comparative images. The user 200 can select the golf club 13 suitable for the user 200 by selecting a second golf club 13 so that at least one of the comparative items of the relative rotation angle θ in a first golf club 13 which is felt to be appropriate matches the comparative item in the second golf club.

FIG. 11 illustrates a case where a plurality of persons perform swings by using the same golf club 13. In other words, a swing performed by a user A by using the golf club 13 is compared with swings performed by a user B and a user C by using the same golf club 13 as reference swings.

As illustrated in FIG. 11, regarding the user A and the user B, time required for the relative rotation angle θ to become the maximum is the same as each other, but the maximum value of the relative rotation angle θ for the user B (θ1B) is greater, and a range of the relative rotation angle θ for the user A (θ2A) is wider. When the user C (θ1C) is compared with the users A and B, the time required for the relative rotation angle θ to become the maximum is smaller, and the maximum value (θ2C) of the relative rotation angle θ is greater.

As mentioned above, since transition of the relative rotation angle θ differs depending on an individual difference even in the same golf club 13, for example, it is possible to improve a swing action of the user 200 by selecting other golf clubs 13 or by adjusting a balance or the like of the golf club 13 so that at least one of the comparative items of the relative rotation angle θ matches that for an instructor or a professional golfer who is a role model.

Referring to FIG. 7 again, the calculation processing circuit 14 includes a rendering portion 41. The rendering portion 41 is connected to the first image data generation portion 33, the comparison calculation portion 39, and the swing image data generation portion 35. Output data from the first image data generation portion 33 and the swing image data generation portion 35 is supplied to the rendering portion 41. The rendering portion 41 generates image data for rendering a comparative image or a swing image on the basis of the output data supplied from the first image data generation portion 33 or the swing image data generation portion 35. The rendering portion 41 generates image data for rendering a comparison result with text information on the basis of the output from the comparison calculation portion 39. The image data generated by the rendering portion 41 is converted into an image signal in the image processing circuit 18, and is then displayed on the display device 19.

The functions (motion analysis method) realized by the calculation processing circuit 14 are not limited to an aspect in which corresponding hardware is individually mounted in each functional portion, and are preferably realized in cooperation between general purpose hardware such as a processor and software. In this case, some of the functions are realized by executing a motion analysis program which is software for analyzing a golf swing. The motion analysis program may be installed in a computer via a recording medium such as a flash memory.

According to the above-described embodiment, the following effects are achieved.

(1) Since a change in a relative rotation angle from a top to impact in a swing rhythm is compared between a swing action using the golf club 13 and a reference swing, and a comparison result is displayed in a graph over time, it is possible to clearly show a difference in transition of the relative rotation angle between the swing using the golf club 13 and the reference swing.

(2) It is possible to select the golf club 13 appropriate for the user 200 by using swing actions using various golf clubs 13 as reference swings.

(3) It is possible to understand differences from other users' swings with swing actions performed by a plurality of users using the same golf club 13 as reference swings.

As mentioned above, the invention has been described on the basis of the illustrated embodiment, but the invention is not limited to the embodiment, and may include the following modification examples.

(1) The calculation portion 38 extracts a corresponding change amount of the relative rotation angle θ from a top to impact, sets the top corresponding to a first state to an initial value, and calculates the relative rotation angle θ over time from the top to the impact corresponding to a second state, but any other configuration may be employed. For example, there may be an aspect in which address is set as a first state, and a top is set as a second state. There may be an aspect in which the first state and the second state can be changed, and are set before the user 200 performs a swing.

(2) There may be an aspect in which the golf club 13 is fitted on the basis of a comparative image with a reference swing. In other words, there may be an aspect in which the golf swing analysis apparatus 11 is provided in a golf shop or the like, and, regarding the golf club 13 with which the user 200 visiting the golf shop performs trial hitting, the golf club 13 is selected so that comparative items match each other between transition (first transition) of the relative rotation angle θ from a top to impact and transition (second transition) of a reference swing, or characteristics of the golf club 13 are adjusted by adding or removing a weight to or from the club head 13 c.

(3) There may be an aspect in which comparative image data or text data rendered by the rendering portion 41 is transmitted to a server connected to a network through communication. There may also be an aspect in which an information processing apparatus which can perform communication with the server is provided in a shop selling the golf club 13, comparative image data or text information of a comparison result transmitted from the golf swing analysis apparatus 11 provided in a home or the like of the user 200 is uploaded to the information processing apparatus of the shop, and a salesperson of the shop selects the golf club 13 appropriate for the user 200 or recommends the golf club 13 suitable for the user 200 on the basis of comparison results or transition of the relative rotation angle θ.

For example, there may be an aspect in which data regarding transition or the like of the relative rotation angle θ of a professional golfer is accumulated in the server, and is downloaded to the computer of the user 200 as a reference swing on the basis of an operation from the golf swing analysis apparatus 11, so that the user 200 practices a swing by referring to the data of the professional golfer at home.

(4) There may be an aspect in which the computer forming the golf swing analysis apparatus 11 is a highly functional mobile phone such as a smart phone or a multi-function mobile terminal such as a tablet PC. There may be an aspect in which the computer is a head mounted display or smart glasses. In other words, the computer may be worn in the same manner as goggles or glasses, and cause virtual image light based on the image data to be incident to the eye of the user 200 so that a comparative image or the like is visually recognized.

The computer may be a wrist device such as a wristwatch provided with a screen for displaying a comparative image or the like. There may be a so-called standalone aspect in which functions of the computer are installed in a casing including the inertial sensor 12, and the casing is attached to the golf club 13.

(5) In the above-described embodiment, the golf swing analysis apparatus analyzing a golf swing has been exemplified, but the invention is applicable to an analysis apparatus analyzing a swing in various sports such as tennis or baseball.

The apparatus performing the above-described method may be implemented by a single apparatus, may be implemented in combination of a plurality of apparatuses, and includes various aspects.

The entire disclosure of Japanese Patent Application No. 2016-029616 filed Feb. 19, 2016 is expressly incorporated by reference herein. 

What is claimed is:
 1. A motion analysis apparatus comprising: a detection portion that detects a state of a shaft of an exercise equipment by using an output from an inertial sensor; a calculation portion that calculates a relative rotation angle of the shaft which changes about an axis of the shaft until the shaft transitions from a first state to a second state due to a swing of the exercise equipment; and a comparison calculation portion that compares the relative rotation angle calculated by the calculation portion with a reference relative rotation angle in a reference swing which is used as a reference, with respect to at least one of a change range of the relative rotation angle, the required time from the first state to a state in which the relative rotation angle becomes the maximum, and the maximum value of the relative rotation angle, and outputs a comparison result.
 2. The motion analysis apparatus according to claim 1, wherein the exercise equipment is a golf club, and wherein the first state is a top state, and the second state is an impact state.
 3. The motion analysis apparatus according to claim 2, wherein the reference swing is a swing using a golf club which is different from the golf club.
 4. The motion analysis apparatus according to claim 2, wherein the reference swing is a swing performed by a user who is different from a user performing the swing.
 5. The motion analysis apparatus according to claim 1, wherein the comparison calculation portion normalizes the relative rotation angle in the first state as an initial value, and compares a relative rotation angle calculated with the passage of transition time from the first state to the second state, with the reference relative rotation angle.
 6. The motion analysis apparatus according to claim 1, further comprising: a display portion that displays the comparison result.
 7. A motion analysis system comprising: the motion analysis apparatus according to claim 1; and an inertial sensor.
 8. A motion analysis system comprising: the motion analysis apparatus according to claim 2; and an inertial sensor.
 9. A motion analysis system comprising: the motion analysis apparatus according to claim 3; and an inertial sensor.
 10. A motion analysis system comprising: the motion analysis apparatus according to claim 4; and an inertial sensor.
 11. A motion analysis system comprising: the motion analysis apparatus according to claim 5; and an inertial sensor.
 12. A motion analysis system comprising: the motion analysis apparatus according to claim 6; and an inertial sensor.
 13. A motion analysis method comprising: detecting a state of a shaft of an exercise equipment by using an output from an inertial sensor; calculating a relative rotation angle of the shaft which changes about an axis of the shaft until the shaft transitions from a first state to a second state due to a swing of the exercise equipment; and comparing the calculated relative rotation angle with a reference relative rotation angle in a reference swing which is used as a reference, with respect to at least one of a change range of the relative rotation angle, the required time from the first state to a state in which the relative rotation angle becomes the maximum, and the maximum value of the relative rotation angle, and outputting a comparison result.
 14. A recording medium recording a program causing a computer to execute: detecting a state of a shaft of an exercise equipment by using an output from an inertial sensor; calculating a relative rotation angle of the shaft which changes about an axis of the shaft until the shaft transitions from a first state to a second state due to a swing of the exercise equipment; and comparing the calculated relative rotation angle with a reference relative rotation angle in a reference swing which is used as a reference, with respect to at least one of a change range of the relative rotation angle, the required time from the first state to a state in which the relative rotation angle becomes the maximum, and the maximum value of the relative rotation angle, and outputting a comparison result.
 15. A display method comprising: displaying transition of a relative rotation angle of a shaft which changes about an axis of the shaft until the shaft transitions from a first state to a second state due to a swing of an exercise equipment, and reference transition of a relative rotation angle in a reference swing which is used as a reference, in an overlapping manner by normalizing the relative rotation angle in the first state as an initial value. 